Susceptibility to insulin dependent diabetes (IDD) in man is highly linked to the class II major histocompatibility complex (MHC) alleles HLA-DR3 and DR4. However, out of the general population, few people with these high risk alleles actually get IDD. The current proposal hypothesizes that there are polymorphisms of class II MHC alleles that specifically associate with IDD. Such polymorphisms are expected to be detectable on the genomic level. This hypothesis will be addressed in the spontaneously diabetic BB rat. In this model of human IDD, diabetes is linked to the rat's MHC, RT-1Mu. We will search for diabetes-specific RT-1Mu polymorphisms using molecular biology approaches by studying the rat genome for class II MHC restriction fragment length polymorphisms using class II cDNA probes. We currently have human and murine cDNA probes for ABeta, AAlpha, EBeta and EAlpha-like genes. Using chromosome walking techniques, the DNA regions flanking our present probes will be explored for genes that might more specifically associate with IDD. This will involve the generation of a lambda genomic library from a diabetic BB rat and identification of single copy sequences in clones recognized by our present probes. Finally, we will search for aberrant class II gene expression (translation [mRNA] and transcription [class II cell surface antigens]) in pancreatic beta cells. Such an occurence might initiate the autoimmune process that produces pancreatic beta cell damage culminating in IDD. Completion of this grant proposal will allow Dr. Winter to become an independent investigator in the the study of the molecular biology and molecular genetics of IDD. Dr. Winter has displayed significant early success in the proposed study as is evident from the data presented in the preliminary results section. Although sharing a common serologically defined RT-1Mu haplotype, on a genomic level, Wistar Furth and BB rats are polymorphic using ABeta probe. Furthermore, in studying BB rats, there are restriction fragment length polymorphisms that may correlate with IDD. Dr. Winter has strong support for his proposal from the Department of Pathology and from his joint sponsors, Dr. Noel Maclaren (autoimmune and HLA aspects of IDD) and Dr. Edward Wakeland (immunogenetics and molecular biology). All facilities required for completion of the proposed research are available within the Health Center at the University of Florida.